Activities can be uploaded to Map My Tracks in GPX, FIT, TCX, CRS or SRM file formats.
It's important to ensure that GPX files use the GPX track format, not the GPX waypoint format, and that the GPX data includes time data. The time data is used to provide a real-time replay of the activity.
Files can be uploaded via the website at Upload > GPX, FIT, TCX, SRM, CRS
Files can also be uploaded by emailing the file to your Map My Tracks dropbox email address. Each person is provided with a personalised email address that lets you send compatible files as attachments to Map My Tracks.
You can find your personalised email address at Settings > Account settings